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    Bioflavour production from tomato and pepper pomaces by Kluyveromyces marxianus and Debaryomyces hansenii
    (Springer, 2015) Guneser, Onur; Demirkol, Asli; Yuceer, Yonca Karagul; Togay, Sine Ozmen; Hosoglu, Muge Isleten; Elibol, Murat
    Bioflavours are called natural flavour and/or fragrance compounds which are produced using metabolic pathway of the microorganism and/or plant cells or their enzyme systems with bioengineering approaches. The aim of this study was to investigate bioflavour production from tomato and red pepper pomaces by Kluyveromyces marxianus and Debaryomyces hansenii. Obtained specific growth rates of K. marxianus and D. hansenii in tomato pomace were 0.081/h and 0.177/h, respectively. The bioflavour profile differed between the yeasts. Both yeasts can produce esters and alcohols such as phenyl ethyl alcohol, isoamyl alcohol, isoamyl acetate, phenyl ethyl acetate and isovaleric acid. Tarhana and rose were descriptive flavour terms for tomato and pepper pomaces fermented by K. marxianus, respectively. Tomato pomace fermented by D. hansenii had the most intense green bean flavour while fermented vegetable and storage/yeast were defined as characteristic flavour terms for pepper pomaces fermented by D. hansenii.
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    Biosynthesis of eight-carbon volatiles from tomato and pepper pomaces by fungi: Trichoderma atroviride and Aspergillus sojae
    (Soc Bioscience Bioengineering Japan, 2017) Guneser, Onur; Yuceer, Yonca Karagul
    The aim of this study was to investigate the possibility of using tomato and red pepper pomaces for the production eight-carbon volatiles by Trichoderma atroviride and Aspergillus sojae. The fermentation of tomato and pepper pomace based media by both moulds was conducted in shake flasks and bioreactors. Microbial growth behaviours and fermentation abilities of T. atroviride and A. sojae under both fermentation conditions were followed by microbial counting. The production of flavours from tomato and pepper pomaces by fungal metabolism was determined by gas chromatography olfactometry, gas chromatography-mass spectrometry and sensory analysis. The results showed that T. atroviride grew faster than A. sojae, and the survival of T. atroviride in the tomato pomace was longer than that of A. sojae. However, T. atroviride grew slower than A. sojae in the pepper pomace. Eight-carbon flavour compounds, including (Z)-1,5-octadien-3-ol, 1-octen-3-ol, (E)-2-octenal and (E)-2-octenol, were produced by T. atroviride and A. sojae from the tomato and pepper pomaces. The highest production levels (265.55 +/- 2.79 and 187.47 +/- 0.92 mu g kg(-1)) were observed for 1-octen-3-ol in the tomato fermentation by T. atroviride and A. sojae, respectively. The relationships between volatile compounds and their flavour characteristics in tomato and pepper pomaces were analysed using principal component analysis. (C) 2017, The Society for Biotechnology, Japan. All rights reserved.
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    Characterisation of aroma-active compounds, chemical and sensory properties of acid-coagulated cheese: Circassian cheese
    (Wiley, 2011) Guneser, Onur; Yuceer, Yonca Karagul
    The objectives of this study were to determine basic composition, aroma and sensory characteristics of Circassian cheese. Seven Circassian cheeses were provided by local producers. Aroma compounds were extracted by using solid-phase microextraction procedure and determined by gas chromatography-olfactometry system. Water-soluble, trichloroacetic acid-soluble and phosphotungstic acid-soluble nitrogen fractions ranged between 2.30-29.35%, 2.48-9.96% and 3.33-6.26%, respectively. Diacetyl, butyric acid, 2-acetyl-1-pyrroline, 1-octen-3-one and methional were identified at high intensities in cheeses. In addition, 'cooked', 'whey', 'creamy' and 'fermented' were defined as characteristic flavour terms for Circassian cheeses.
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    Characterization of volatiles in Beaten cheeses Bieno sirenje by SPME/GC-MS: Influence of geographical origin
    (Serbian Chemical Soc, 2014) Sulejmani, Erhan; Rafajlovska, Vesna; Guneser, Onur
    In this study, the volatile profiles of an economically important type of cheeses for the FYR Macedonian dairy sector were characterized. A total of eighteen samples belonging to 6 different geographical regions of Beaten cheese, including cheeses from Kumanovo, Tetovo, Struga, Resen, Veles and Radovis, were comparatively studied for their volatile profiles. Sixty one volatile compounds were identified in the cheeses by solid-phase micro-extraction combined with gas chromatography mass spectrometry. The results are discussed based on their chemical classes (17 esters, 9 ketones, 10 acids, 8 alcohols, 6 terpenes and 11 miscellaneous compounds). Acids, esters and alcohols were the most abundant classes identified and were highly dependent on the geographical origin of the cheeses. Beaten cheese from Struga had the highest levels of carboxylic acids, ketones, alcohols, esters and terpenes. The Beaten cheese of other geographical origin had low levels of volatiles, probably due to the effects of the variable characteristics of the employed milk and differences in the cheese making processes, which affected the biochemical processes. The results suggested that each cheese from different geographical regions had a different volatiles profile and that the manufacturing technique and the ripening stage of the cheeses played major roles in determining the distribution of the volatile compounds.
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    Cold pressed capia pepperseed (Capsicum Annuum L.) oils: Composition, aroma, and sensory properties
    (Wiley, 2015) Yılmaz, Emin; Arsunar, Emel Sevgi; Aydeniz, Buket; Guneser, Onur
    In this study, cold press-produced capia pepperseed oil samples were characterized. Pre-roasting and enzyme treatment against control group (no pre-treatment) were applied to the seeds prior to cold pressing, and the oil yield, meal, and oil quality parameters were examined. The physico-chemical parameters (refractive index, viscosity, turbidity, specific gravity, color, free acidity, peroxide and iodine values, antioxidant capacity, total phenolic content, and energy value), components composition (fatty acid, sterol, and tocopherol), thermal parameters (melting and crystallization temperatures and enthalpies), volatile aromatics composition, sensory properties (Flavor Profile Analysis), and consumer perception (hedonic test) of the oil samples were accomplished. It was found that cold pressing is low in efficiency, and oil sensory quality and consumer acceptability levels were also low. Although pre-roasted seeds yielded a little more oil and had better sensory quality, it was determined that these oils need at least a deodorization or a physical refining for acceptable sensory quality. Practical applications: The results of this study indicated that capia pepperseeds obtained as waste during vegetable processing can be used as an alternative source for cold pressed oils and a raw material for animal feed. Moreover, these seed oils have economical impact due to their essential fatty acid (linoleic acid, 71.13%), sterol, and tocopherol content. Based on the sensory findings, full or partial refining is recommended in order to increase the sensory quality of the pepperseed oil.
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    Different Bioengineering Approaches on Production of Bioflavor Compounds
    (Elsevier, 2018) Hosoglu, Muge I.; Guneser, Onur; Yuceer, Yonca K.
    Flavor compounds are generally used as food additives and mostly produced through artificial means-that is, chemical synthesis or by extraction from plant and animal sources. The increasing consumer preference for natural products has promoted significant efforts toward the biotechnological production of these compounds (bioflavor). There are two kinds of aroma and flavor production via biotechnological process, de novo microbial processes and bioconversions of natural precursors using microbial cells or enzymes. The production of bioflavors with microorganisms and enzymes is illustrated by the discussion of the current state of the art developments in this field. Efforts at production of flavor compounds often lack economic profitability, mainly due to low productivities or low concentrations of target compounds in fermentation broth. This chapter reviews also the current state of the art of bioprocess used for the production of flavor and fragrance compounds, with emphasis on different ways used to improve process productivity. Bioengineering provides promising technical options for increasing the productivity with bioflavor production, such as different fermentation strategies (batch, fed-batch, and continuous fermentation), gas-phase or two-phase reactions, specific reactor constructions such as membrane, solid-state or closed loop reactors, optimization and modeling approaches of bioprocess and in situ recovery of product. © 2018 Elsevier Inc. All rights reserved.
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    Effect of emulsifiers on oil separation problem and quality characteristics of Tahin Helva during storage
    (Springer India, 2014) Guneser, Onur; Zorba, Murat
    Tahin helva is one of Turkish traditional confectionary foods. Sesame paste, sugar syrup and soapwort extract were used for tahin helva's production. The purpose of this study was to solve the oil separation problem occurred in tahin helva by using food additives permitted as an emulsifier for tahin helva in the Turkish and EU Codex. Sorbitan tristearate (STS), sorbitan monopalmitate (SMP) and their combinations (STS:SMP, 1:1) were added to tahin helva, then helva samples were stored at the storage temperatures of 20 A degrees C, 30 A degrees C, and 40 A degrees C. The emulsifiers did not have any effect on physical, chemical and sensory properties of tahin helva except on its oil content, whereas storage temperature and storage time had effects on those properties of helva. STS:SMP combination was found to be statistically more effective than SMP and STS formulations in preventing oil separation. Penetration force of tahin helva has increased by increasing the storage temperature and storage time. It was found that there was a decrease in -a colour value of helva through the storage time at 20 A degrees C and 30 A degrees C, while there was an increase in that value at 40 A degrees C. The highest change in the moisture content of all helva samples through storage was observed at the storage temperature of 20 A degrees C. Sensory scores for appearance, texture and flavour characteristics of helva have decreased significantly during the storage period.
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    ENGINEERING OF MILK-BASED BEVERAGES: CURRENT STATUS, DEVELOPMENTS, AND CONSUMER TRENDS
    (Woodhead Publ Ltd, 2019) Guneser, Onur; Hosoglu, Muge Isleten; Guneser, Buket Aydeniz; Yuceer, Yonca Karagul
    [Anstract Not Available]
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    Evaluation of physicochemical, microbiological, sensory properties and aroma profiles of goat cheeses provided from Canakkale
    (Wiley, 2017) Togay, Sine Ozmen; Guneser, Onur; Yuceer, Yonca Karagul
    The purpose of this study was to determine physicochemical and sensory properties, aroma-active compounds and number of lactic acid bacteria in goat cheeses. High variation was observed among the cheeses in terms of fat %(w/w) and salt %(w/w) contents and titratable acidities %(w/w). Average counts of lactococci lactobacilli and enterococci were 6.90, 6.43 and 5.26log cfu (colony-forming unit)/g, respectively. The following compounds had high aroma intensity in the cheeses: acetic acid, butanoic acid, hexanoic acid, p-cresol and phenyl acetic acid. Cooked, whey, creamy, animal-like, waxy, salty and sour were the characteristic sensory descriptors.
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    Evaluation of Some Physical, Chemical and Sensory Properties of Kasar Cheese and Its Processed and Analogue Types
    (Galenos Publ House, 2017) Yalman, Musa; Guneser, Onur; Karagul Yuceer, Yonca
    The objective of this study was to evaluate the changes in physical, chemical and sensory properties of the kasar cheese and its processed and analogue types during 90-day storage. Aroma-active compounds in the cheeses were identified by gas chromatography-olfactometry. Sensory properties of the cheeses were determined by descriptive sensory analysis. Differences in basic composition of the cheeses were found. There were also significant differences among the cheeses in terms of meltability, oil separation index, L* and a* values. Whey, cooked, creamy and fermented were the most intense sensory descriptors in the cheeses analyzed on days 1 and 30. However, waxy and animal intensities were much higher in analogue cheese than others. 18 aroma-active compounds were determined in the cheeses during 90 day storage. Diacetyl, acetic acid, butyric acid, 2-/3-methyl butyric acid, 2-acetyl-2-thiazoline, beta-ionene, 2-phenylethyl alcohol, maltol, p-cresol, sotolon, delta-decalactone and gamma-dodecalactone were some of the characteristic aroma-active compounds. Kasar cheese was the most liked cheese while analogue cheese was the least liked cheese by consumers.
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    Fermented Spirulina products with Saccharomyces and non- Saccharomyces yeasts: Special reference to their microbial, physico-chemical and sensory characterizations
    (Elsevier, 2022) Sahin, Busra; Hosoglu, Muge Isleten; Guneser, Onur; Karagul-Yuceer, Yonca
    Innovative products produced from various sources through fermentation processes have been a resurgence of interest. This study was designed to determine the performance of fermented Spirulina (FS) products by three different yeast species including Debaryomyces hansenii, Kluyveromyces marxianus and Saccharomyces cerevisiae and investigate the microbial, physicochemical and sensory characteristics of products. The results showed that the increase in yeast cell number was around 3 log after 48 h fermentation in Spirulina medium without additional carbon source. Protein bands with a molecular weight of-51 kDa seemed less visible and bands 14-22 kDa disappeared after 48 h fermentation by K. marxianus showed strong hydrolysis of proteins during fermentation. The amino acid compositions of the three kinds of FS were different also compared to unfermented Spirulina (unFS). Glutamic acid, methionine, lysine, isoleucine and valine became more dominant in FS samples. According to GC-MS analysis, there was a decrease in the concentration of pyrazine, ketone and aldehyde compounds of FS compared to unFS. The flavor notes of seaweed, cardboard, earthy/muddy and cereal/ straw were found to be the highest in unFS than in FS detected by panelists during sensory evaluations. FS by K. marxianus is highly characterized as having the lowest seaweed and umami flavor attributes and higher fermented and rose attributes. Finally, the current study revealed that the potential of Spirulina biomass to be a suitable substrate for yeasts and fermentation of Spirulina with different yeast species led to different kinds of products.
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    Formation kinetics of hydroxymethylfurfural and brown coloured compounds in goat milk during heating
    (Wiley, 2013) Guneser, Onur; Toklucu, Aysegul Kirca; Karagul-Yuceer, Yonca
    The formation of hydroxymethylfurfural, nonenzymatic brown coloured compounds and free sulphydryl groups in goat milk was studied during heating at 7595 degrees C. Analysis of kinetic data suggested that formation of hydroxymethylfurfural and nonenzymatic brown coloured compounds followed zero order reaction kinetics, while formation of free sulphydryl groups during heating varied depending on heating time. A good linear correlation (r = 0.839) was found between brown coloured compounds and hydroxymethylfurfural content in milk samples during heating. Activation energies (Ea) for the formation of hydroxymethylfurfural and nonenzymatic brown coloured compounds were 96.31 and 69.79 kJ/mol, respectively.
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    Growth and by-product profiles of Kluyveromyces marxianus cells immobilized in foamed alginate
    (Wiley, 2015) Wilkowska, Agnieszka; Kregiel, Dorota; Guneser, Onur; Yuceer, Yonca Karagul
    The aim of this research was to study how the yeast cell immobilization technique influences the growth and fermentation profiles of Kluyveromyces marxianus cultivated on apple/chokeberry and apple/cranberry pomaces. Encapsulation of the cells was performed by droplet formation from a foamed alginate solution. The growth and metabolic profiles were evaluated for both free and immobilized cells. Culture media with fruit waste produced good growth of free as well as immobilized yeast cells. The fermentation profiles of K. marxianus were different with each waste material. The most varied aroma profiles were noted for immobilized yeast cultivated on apple/chokeberry pomace. Copyright (c) 2014 John Wiley & Sons, Ltd.
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    Influence of carbon and nitrogen source on production of volatile fragrance and flavour metabolites by the yeast Kluyveromyces marxianus
    (Wiley, 2015) Gethins, Loughlin; Guneser, Onur; Demirkol, Asli; Rea, Mary C.; Stanton, Catherine; Ross, R. Paul; Yuceer, Yonca
    The yeast Kluyveromyces marxianus produces a range of volatile molecules with applications as fragrances or flavours. The purpose of this study was to establish how nutritional conditions influence the production of these metabolites. Four strains were grown on synthetic media, using a variety of carbon and nitrogen sources and volatile metabolites analysed using gas chromatography-mass spectrometry (GC-MS). The nitrogen source had pronounced effects on metabolite production: levels of the fusel alcohols 2-phenylethanol and isoamyl alcohol were highest when yeast extract was the nitrogen source, and ammonium had a strong repressing effect on production of 2-phenylethyl acetate. In contrast, the nitrogen source did not affect production of isoamyl acetate or ethyl acetate, indicating that more than one alcohol acetyl transferase activity is present in K. marxianus. Production of all acetate esters was low when cells were growing on lactose (as opposed to glucose or fructose), with a lower intracellular pool of acetyl CoA being one explanation for this observation. Bioinformatic and phylogenetic analysis of the known yeast alcohol acetyl transferases ATF1 and ATF2 suggests that the ancestral protein Atf2p may not be involved in synthesis of volatile acetate esters in K. marxianus, and raises interesting questions as to what other genes encode this activity in non-Saccharomyces yeasts. Identification of all the genes involved in ester synthesis will be important for development of the K. marxianus platform for flavour and fragrance production. Copyright (c) 2014 John Wiley & Sons, Ltd.
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    Influence of Storage on Physicochemical and Volatile Features of Enriched and Aromatized Wax Organogels
    (Wiley, 2015) Ogutcu, Mustafa; Yılmaz, Emin; Guneser, Onur
    In this study, virgin olive oil (VOO) organogels were produced with beeswax (BW) and sunflower wax (SW) and enriched with beta-carotene, vitamin D-3 and E as well as aromatized with strawberry, banana, and butter aromas. The physicochemical, thermal, structural, and sensorial properties of the fresh organogel samples were determined. The peroxide values, antioxidant activities, firmness, and volatile compositions of the fresh samples and those stored for 3 months were also determined. The organogels were not only stable, uniform, and homogenous during the storage period but also the added components did not affect the organogel properties. The panel defined three appearance, four texture, three mouthfeel, four aroma, and four flavor terms to describe the organogels sensorially. Moreover, the added aroma (banana, strawberry, and diacetyl-butter) components of the fresh and stored organogels were quantified by GC/MS-SPME. In conclusion, these results demonstrated that beeswax and sunflower wax are very suitable to preserve the aromatic characteristics of these types of spreadable products.
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    Investigation of antimicrobial activity and entA and entB genes in Enterococcus faecium and Enterococcus faecalis strains isolated from naturally fermented Turkish white cheeses
    (Korean Society Food Science & Technology-Kosfost, 2016) Togay, Sine Ozmen; Ay, Mustafa; Guneser, Onur; Yuceer, Yonca Karagul
    In this research, the antagonistic effects of Enterococcus faecalis and E. faecium bacteria isolated from naturally fermented Turkish white cheeses, produced without starter culture, against Listeria monocytogenes, L. innocua, L. ivanovii, Staphylococcus aureus, and E. faecalis were evaluated. The presence of entA and entB genes was also detected in the isolates, which had antimicrobial activity. Total 71 strains of E. faecalis and 7 strains of E. faecium were tested; 20 of E. faecalis and none of E. faecium strains showed antimicrobial activity against the tested bacteria using agar spot method. Among E. faecalis strains, which had antimicrobial activity, three strains contained both entA and entB genes, two strains carried only entA gene, and five strains had only entB gene. These cheese-sourced enterococcal strains or their enterocins should be considered to be used for food preservation especially in the dairy industry.
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    Optimizing bioreactor conditions for Spirulina fermentation by Lactobacillus helveticus and Kluyveromyces marxianus: Impact on chemical & bioactive properties
    (Elsevier Sci Ltd, 2024) Yay, Cansu; Cinar, Zeynep Ozlem; Donmez, Serhat; Tumer, Tugba Boyunegmez; Guneser, Onur; Hosoglu, Muge Isleten
    This study focused on optimizing the production of fermented Spirulina (FS) products using a bioactivity-guided strategy with Lactobacillus helveticus B-4526 and Kluyveromyces marxianus Y-329 in a 3-L bioreactor. Various operating conditions, including aeration rates and pH modes, were tested. While both microorganisms thrived under all conditions, the cascade mode, controlling dissolved oxygen, enhanced protein hydrolysis and antioxidant activity, as confirmed by SDS-PAGE and DPPH/TEAC assays, respectively. Screening revealed that cascade FS significantly decreased viability of colon cancer cells (HT-29) in a dose-dependent manner, with up to a 72 % reduction. Doses <= 500 mu g mL- 1 of cascade FS proved safe and effective in suppressing NO release without compromising cellular viability. Additionally, cascade FS exhibited diverse volatile organic compounds and reducing the characteristic seaweed aroma. These findings highlight cascade FS as a promising alternative food source with improved bioactive properties, urging further exploration of its bioactive compounds, particularly bioactive peptides.
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    Physico-chemical, Sensory and Aromatic Properties of Cold Press Produced Safflower Oil
    (Springer, 2014) Aydeniz, Buket; Guneser, Onur; Yılmaz, Emin
    In this study, seeds from the safflower variety called Din double dagger er were roasted and microwaved before oil extraction by cold pressing. Some physico-chemical analyses (moisture, ash, oil content and color) were performed in safflower meals. Physico-chemical properties (refractive index, viscosity, turbidity, specific gravity, color, free acidity, peroxide value, iodine number), nutritional components (total phenolics, antioxidant capacity, tocopherol content), sterol composition and fatty acid composition of produced oils were also determined. Volatile components of the oils were detected by solid-phase microextraction/gas chromatography-mass spectrometry technique. Quantitative descriptive analysis was accomplished with trained panelists by 11 definition terms. Cold pressing yielded less oil than solvent extraction, but oil quality was superior and a refining process was not required. There was no significant difference between samples for fatty acid composition and some physico-chemical parameters. Whereas, microwave treatment caused a decrease in oil turbidity, free acidity, alpha-tocopherol and some sterol contents and an enhancement in total phenolic content, antioxidant capacity and peroxide value. Moreover, microwave treatment led to an increased nutty aroma in the oil. In contrast, isot pepper aroma was decreased by microwave treatment. This study provides very important information about the safflower oils for the first time in the literature.
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    Production of flavor compounds from olive mill waste by Rhizopus oryzae and Candida tropicalis
    (Soc Brasileira Microbiologia, 2017) Guneser, Onur; Demirkol, Asli; Yuceer, Yonca Karagul; Togay, Sine Ozmen; Hosoglu, Muge Isleten; Elibol, Murat
    The purpose of this study was to investigate the production of flavor compounds from olive mill waste by microbial fermentation of Rhizopus oryzae and Candida tropicalis. Olive mill waste fermentations were performed in shake and bioreactor cultures. Production of flavor compounds from olive mill waste was followed by Gas Chromatography Mass spectrometry, Gas chromatography- olfactometry and Spectrum Sensory Analysis. As a result, 1.73-log and 3.23-log cfu/mL increases were observed in the microbial populations of R. oryzae and C. tropicalis during shake cultures, respectively. C. tropicalis can produce a higher concentration of n-limonene from olive mill waste than R. oryzae in shake cultures. The concentration of n-limonene was determined as 185.56 and 249.54 mu g/kg in the fermented olive mill waste by R. oryzae and C. tropicalis in shake cultures respectively. In contrast, R. oryzae can produce a higher concentration of n-limonene (87.73 mu g/kg) n-limonene than C. tropicalis (11.95 mu g/kg) in bioreactor cultures. Based on sensory analysis, unripe olive, wet towel, sweet aromatic, fermented aromas were determined at high intensity in olive mill waste fermented with R. oryzae meanwhile olive mill waste fermented with C. tropicalis had only a high intensity of unripe olive and oily aroma. (C) 2016 Sociedade Brasileira de Microbiologia. Published by Elsevier Editora Ltda.